Flow control device, introducer and method of implanting

ABSTRACT

An implant having a tube for permitting fluid flow has an outer flange at the outlet end and a retention projection near the inlet end. A delivery device for implanting the implant has a central bore for accommodating the implant during the implantation procedure. When the implant is loaded in the delivery device, the retention projection of the implant protrudes beyond the outside surface of the delivery device. After the delivery device and implant have penetrated the tissue through which drainage is desired, and the retention projection has fully penetrated through the tissue, the delivery device is withdrawn. The retention projection acts as a hook engaging the inside surface of the tissue, causing the implant to stay implanted in the tissue. An implant may also be provided with a mechanism for temporary occlusion, in whole or in part, of the flow passage. Thus, the tube passage may be filled, partially or wholly, with absorbable material and/or a plurality of withdrawable or advanceable flow controlling strands.

FIELD OF THE INVENTION

[0001] The invention relates generally to medical implants used toregulate the flow of fluids within the body. The invention may beapplied, for example, to ophthalmic implants for treatment of glaucoma.The invention also relates to delivery devices for implanting suchimplants, to methods of implanting such implants, and to methods ofmanufacturing such implants.

BACKGROUND OF THE INVENTION

[0002] Medical implants used to regulate the flow of fluids within thehuman body are known and used. One application for the use of suchimplants is in the treatment of glaucoma. Typical ophthalmic implantsutilize drainage tubes for the release of aqueous humor from the eye torelieve the intraocular pressure (IOP).

[0003] Several disadvantages have at times been associated with priorimplants. For example, implants using valve mechanisms to regulate fluidflow have risked malfunction due to defects in and/or failure of suchvalve mechanisms. Depending on such factors as the site of implantation,some implants have tended to clog while in use due to tissue coveringthe inlet end or the outlet end of the drainage tube. In addition, priorimplants at times have required insertion operations that arecomplicated, costly, and time-consuming, for example requiring suturingof the implant once it is in place.

PATENTS AND APPLICATIONS INCORPORATED BY REFERENCE

[0004] The assignee of this patent application is also the assignee ofother patents and patent applications describing and illustratingimplants directed at overcoming some of the drawbacks associated withprior implants, as well as delivery devices for such implants, methodsof using such implants, and methods of manufacturing such implants.

[0005] For example, implants, delivery devices, methods of use, andmethods of manufacturing are described and illustrated in U.S. Pat. No.5,868,697 and U.S. Pat. No. 5,702,414, both of which are owned by theassignee of this application, and both of which are hereby expresslyincorporated by reference into this application.

[0006] Further examples of such implants, delivery devices, methods ofuse, and methods of manufacturing are also described and illustrated inU.S. patent application Ser. No. 08/975,386, filed Nov. 20, 1997, whichis also owned by the assignee of this application, and which is alsohereby expressly incorporated by reference into this application.

SUMMARY OF THE INVENTION

[0007] One object of the invention is to provide a flow regulatingimplant and an associated delivery device that enable the implant to beinserted in a relatively simple and efficient procedure.

[0008] In one embodiment in accordance with the invention, an implanthaving a tube for permitting fluid flow has an outer flange at theoutlet end and one or more retention projections near the inlet end. Anintroducer or delivery device for implanting the implant has a centralbore for accommodating the implant during the implantation procedure.The implant and delivery device are designed so that when the implant isloaded in the delivery device, the retention projection or projectionsof the implant protrude from the delivery device to act as a hook orhooks during the procedure.

[0009] In accordance with a method of using the implant and deliverydevice according to an embodiment of the invention, the implant isloaded in the delivery device with the retention projection protrudingfrom the delivery device. The delivery device and implant then penetratethe tissue through which drainage is desired, for example, the sclera ofan eye. Once the retention projection has fully penetrated through thetissue, the delivery device is withdrawn. The retention projection actsas a hook engaging the inside surface of the tissue, causing the implantto stay implanted in the tissue when the delivery device is withdrawn.

[0010] The retention projection may be made, for example, of an elasticmaterial, so that it is able to be flexed inward against the tube of theimplant during penetration through the tissue. Alternatively, theretention projection may be designed to lie initially relatively flatagainst the tube for easier penetration and to prevent tearing of thetissue, with a mechanism for extending the retention projectionoutwardly when the implant is implanted.

[0011] Another object of the invention is to provide a simple andefficient method of manufacturing a flow regulating implant. In a methodfor manufacturing an implant according to an embodiment of theinvention, the device may be molded out of a suitable material, forexample, silicone. To provide the tube passage of the implant, a thinwire may be used during the molding process. The implant alternativelymay be constructed out of stainless steel or any other suitablematerial.

[0012] A further object of the invention is to provide a flow regulatingimplant with beneficial flow characteristics. Thus, the implant may havevarious mechanisms for changing the configuration of the flow path. Forexample, a flow controlling rod or other obstruction may be placed inthe tube passage for changing the dimensions within the tube passage.This rod or obstruction may be temporary. For example, it may be made ofabsorbable (biodegradable) material that is eroded and absorbed.Alternatively, it may be constructed in such a way that it may beremoved from the tube passage or advanced into the tube passage at aperiod of time after implantation. For example, one or more strands,such as sutures, may be placed in the tube passage and withdrawn oradvanced by a physician as desired at a later time or times.

[0013] An implant according to the invention has other applicationsaside from the field of intraocular implants. For example, the implantmay be used for drainage of a hydrocele sac, regulating flow between thehydrocele sac and the subcutaneous scrotum. Persons of ordinary skill inthe art will appreciate that other applications of an implant inaccordance with the invention are possible, as are various modificationsof the embodiments described herein, without departing from the scope ofthe invention as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1A is a side view of a first embodiment of a drainageimplant;

[0015]FIG. 1B is an end view of the drainage implant shown in FIG. 1A;

[0016]FIGS. 2A through 2C illustrate a delivery device and insertion ofthe drainage implant of FIG. 1A into desired tissue, with FIG. 2Ashowing the delivery device and implant before insertion, FIG. 2Bshowing the delivery device and implant being placed through the tissue,and FIG. 2C showing the inserted implant after the delivery device hasbeen withdrawn;

[0017]FIG. 3A is a side view of a second embodiment of a drainageimplant;

[0018]FIG. 3B is an end view of the drainage implant shown in FIG. 3A;

[0019]FIG. 3C is a cross-sectional view taken along the plane identifiedby the line 3C-3C in FIG. 3A;

[0020]FIG. 4A is a side view of a third embodiment of a drainageimplant;

[0021]FIG. 4B is an end view of the drainage implant shown in FIG. 4A;

[0022]FIG. 5 illustrates a second embodiment of a delivery device withan implant inserted in the delivery device and with the procedure at astage corresponding to that in FIG. 2B;

[0023]FIG. 6 illustrates an intraocular implant according to theinvention with a flow controlling plug made of absorbable material inthe tube passage;

[0024]FIGS. 7A through 7D illustrate four variations of cross-sectionsfor a flow controlling plug;

[0025]FIG. 8 illustrates an intraocular implant according to theinvention with a flow controlling plug made of absorbable material inthe tube passage and with side holes partially occluded by plugs made ofabsorbable material;

[0026]FIG. 9 illustrates an intraocular implant according to theinvention with flow controlling strands in the tube passage;

[0027]FIG. 10 illustrates an end view of an intraocular implant withflow controlling strands in the tube passage;

[0028]FIG. 11 illustrates an intraocular implant according to theinvention with a knotted flow controlling strand in the tube passage;and

[0029]FIG. 12 illustrates an alternative construction of a flowcontrolling strand.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0030]FIGS. 1A and 1B show a side view and end view, respectively, of afirst embodiment of a drainage implant 10 in accordance with theinvention. The implant 10 has a tube 12 having a tube passage 14 forpermitting fluid flow between an inlet end of the implant and an outletend of the implant. One or more side holes 16 may be provided around thecircumference of the tube 12 near the inlet end, allowing access forfluid flow into the tube passage 14.

[0031] The implant 10 has an outer flange 18 at the outlet end and aretention projection 20 near the inlet end. The plane of the outerflange 18 may form an angle with the tube 12, with the angle selected tocorrespond to the angle between the surface of the tissue into which theimplant 10 is to be inserted and the axis of insertion of the tube 12 ofthe implant 10.

[0032]FIGS. 2A through 2C illustrate an introducer or delivery device 30for implanting the implant 10 and the method of implanting the implant10 with that delivery device 30. The delivery device 30 has handle 32and a tube 34 having a central bore 36 for accommodating the implant 10during the implantation procedure. The delivery device 30 has a beveledtip 38 to allow penetration of the tissue 50 into which the implant isto be inserted. In an alternative embodiment, the implant itselfpenetrates the tissue by its beveled tip at the inlet end.

[0033] An opening 40 is provided in the wall of the tube 34 of thedelivery device 30. In this illustrated embodiment, the opening 40allows both the retention projection 20 and the outer flange 18 toprotrude beyond the wall of the tube 34 when the implant 10 is loaded inthe delivery device 30. Because it projects beyond the wall of the tube34, the retention projection 20 of the implant 10 can act as a hookduring the implantation procedure.

[0034] As can be seen in FIG. 1B, the flange 18 of the implant 10 hasnotches or grooves 19 on either side. These notches or grooves 19correspond approximately to the width of the wall of the tube 34 of thedelivery device 30 and accommodate the wall of the tube 34 of thedelivery device 30 when the implant 10 is loaded in the delivery device30. The notches or grooves 19 may take any suitable shape.Alternatively, the flange 18 may have a continuous width, with nonotches or grooves, with the width of the flange 18 being slightlynarrower than the diameter of the tube 12 of the implant 10. Furthervariations of the configuration of the flange 18 are possible.

[0035] To use the implant 10 and delivery device 30, the implant 10 isloaded in the delivery device 30 with the retention projection 20protruding from the delivery device, as shown in FIG. 2A. The deliverydevice 30, with the implant loaded inside, is then pressed through thetissue 50 through which drainage is desired, for example, the sclera ofan eye. FIG. 2B illustrates the delivery device 30 pressed through thetissue 50.

[0036] To facilitate introduction of the delivery device 30 and/orimplant 10 into the tissue 50, the delivery device 30 may be orientedsuch that the beveled tip 38 forms a sharper angle with the tissue 50.Thus, for example, the delivery device as shown in FIG. 2A may berotated 180 degrees, i.e., with the retention projection 20 facingupward. In the case of an implant 10 being placed into the limbal scleraof an eye, this corresponds to the retention projection 20 being on theopposite side of the tube 12 from the iris. When the delivery device 30and implant 10 are suitably through the tissue 50, they may be rotatedto align the implant 10 properly in the tissue 50, with the flange 18and retention projection 20 oriented as desired with respect to thetissue 50.

[0037] Once the retention projection 20 has fully penetrated through thetissue 50, the delivery device 30 is withdrawn. The retention projection20 acts as a hook engaging the inside surface of the tissue 50, causingthe implant 10 to stay implanted in the tissue 50 when the deliverydevice 30 is withdrawn. FIG. 2C illustrates the implant 10 implanted inthe tissue 50, with the delivery device 30 withdrawn.

[0038] Since the tube 34 of the delivery device 30 is hollow, it may beused to inject fluid or viscoelastic material. Thus, fluid may beinjected into the anterior chamber of an eye upon implantation to reducethe risk of hypotony. Similarly, a viscoelastic material may be injectedunder the conjunctiva to help fill the bleb that exists afterimplantation.

[0039] The implant 10 may be molded out of a suitable material, forexample, silicone. To provide the tube passage 14 of the implant 10, athin wire may be used during the molding process. More than one wire maybe used, in order to have more than one tube passage in the implant. Theimplant alternatively may be constructed out of stainless steel oranother suitable material. It may be coated with a suitableanti-fibrosis material, such as heparin.

[0040] The retention projection 20 may be formed of the same material asthe rest of the implant 10. Alternatively, it may be made of a moreflexible material to allow it to be flexed inward against the tube 12 ofthe implant 10 during penetration through the tissue 50. Alternatively,the retention projection 20 may be designed to lie initially relativelyflat against the tube 12 for easier penetration and to prevent tearingof the tissue 50, to be extended outwardly by an expansion mechanism,for example a balloon, when the implant 10 is implanted.

[0041]FIGS. 3A, 3B and 3C show a side view, end view, and cross-section,respectively, of a second embodiment of a drainage implant 60 inaccordance with the invention. Like the implant 10 shown in FIGS. 1A and1B, the implant 60 in FIGS. 3A, 3B, and 3C has a tube 62 having a tubepassage 64 and side holes 66 opening into the tube passage 64. Theimplant 60 also has an outer flange 68 at the outlet end and a retentionprojection 70 near the inlet end. In this case, the outer flange 68projects beyond the outer surface of the tube 62 in all directionsaround the circumference of the tube 62.

[0042]FIGS. 4A and 4B show a side view and end view, respectively, of athird embodiment of a drainage implant 80, similar to the implant 60shown in FIGS. 3A, 3B, and 3C. The tip 82 of the implant 80 is conical,in contrast to the blunt tip 72 of the implant 60.

[0043] In an alternative construction, the implant may be made with aclosed end with a slit in it. Fluid can only pass through the devicewhen the pressure rises sufficiently to open the slit. Alternatively, adifferent portion along the length of the tube passage may be providedwith such a construction.

[0044]FIG. 5 illustrates an alternative embodiment of a delivery device90 in accordance with the invention. In this embodiment, the opening 92allows only the retention projection 84 of the implant to protrudebeyond the wall of the tube 94 of the delivery device. The outer flange86 is accommodated within the central bore 96 of the delivery device 90.In this embodiment, the outer flange 86 must be folded or bent to beaccommodated within the central bore 96 of the delivery device 90. Theouter flange 86 is resilient, so that when the implant is removed fromthe delivery device, the outer flange 86 extends to a positionrelatively coplanar with the outer surface of the tissue into which theimplant is inserted.

[0045] Similarly, the retention projection 84 may also be constructed tobe sufficiently resilient to allow it to be compressed and completelyaccommodated within the central bore 96 of the delivery device 90. Inaddition, the delivery device 90 may be constructed with the tube 94having a continuous outer wall, with no opening 92. To facilitateremoval of the implant from the delivery device, a pusher rod or wiremay be located within the bore of the delivery device. By advancing thepusher rod or wire within the delivery device against the implant, thephysician can force the implant out of the delivery device, therebyallowing the retention projection to expand outwardly to its initial,relaxed position, enabling it to engage the inside surface of thetissue.

[0046] Various mechanisms may be used, if desired, for giving differentflow characteristics to the implant. It may be desirable to use implantswith different flow characteristics for different patients and/or tohave an implant in which the flow characteristics may be changed afterimplantation in a particular patient.

[0047] U.S. patent application Ser. No. 08/975,386, filed Nov. 20, 1997and incorporated by reference herein, describes and illustrates variousmechanisms for assisting in controlling the flow of fluid, e.g. aqueoushumor, through an implant. It describes and illustrates the use of aflow controlling wire or rod in the tube passage of an implant.

[0048] The effect of the flow controlling rod or wire is to reduce thecross-sectional area through which the fluid flows for a particularlength inside the tube passage of the implant. Because the flow is afunction of the cross-section and length of the lumen through which itpasses, the interposition of the flow controlling rod or wire serves toincrease the resistance to flow. In an intraocular implant, for example,this assists in reducing the risk of hypotony.

[0049] The configuration and dimensions of the flow controlling rod orwire may be selected in accordance with the flow characteristics thatare desired. It may have one or more internal bores or external grooves,any of which may be helically arranged to increase its length. It may beadjustable, by moving it axially or rotating it, to modify the flowcharacteristics. Persons skilled in the art will appreciate thatnumerous other variations are possible for the configuration of the flowcontrolling rod or wire.

[0050] The flow controlling rod or wire may have its axis alignedparallel with the axis of the tube passage, but other orientations arepossible. For example, a flow controlling rod or wire having a diameterslightly smaller that the tube passage may be oriented transverse to thetube passage. The transversely oriented rod or wire will have a shortlength, corresponding approximately to the diameter of the tube or tubepassage. It serves as an obstruction to the flow through the tubepassage, altering the flow characteristics. Other obstruction may beplaced in the tube passage for achieving similar results.

[0051] Another mechanism described and illustrated in U.S. patentapplication Ser. No. 08/975,386 for assisting in controlling the flow offluid through an implant is the use of temporary occlusion. By occludingthe flow passage of the implant with an absorbable material or with amaterial that may be removed after implantation, for example by a toolor laser probe, the resistance to flow can be reduced afterimplantation.

[0052] The use of temporary occlusion is advantageous in situations inwhich flow through the implant is desired to be kept low atimplantation, and possibly also for a period of time after implantation.For example, when an implant is implanted in the eye, the incision inthe conjunctiva and/or possible tearing of the sclera around the implantprovide potential flow passages for aqueous humor. Thus, to reduce therisk of hypotony, it may be desirable to prevent or reduce flow throughthe implant upon implantation and for a period thereafter. Once theconjunctiva and/or sclera have healed, the flow through the implant canbe increased.

[0053] The temporary occlusion need not be limited to any particularpart of the flow passage. For example, the side holes and/or the tubepassage of the implant may be filled, partially or wholly, withabsorbable material. Thus, for example, as shown in FIG. 6, a plug 106Aof absorbable material may be placed in the tube passage 102 of theimplant 100. With an absorbable material that biodegrades by surfaceerosion, as fluid contacts and flows adjacent to the plug 106A, thematerial of the plug 106A is absorbed into the fluid, thereby reducingthe dimensions of the plug 106A. As the dimensions of the plug 106A arereduced, the resistance to flow through the implant is similarlyreduced. Alternatively, an absorbable material that biodegrades by bulkerosion may be used. Absorbable (biodegradable) materials are known andused, and such materials are described, for example, in Middleton &Tipton, “Synthetic Biodegradable Polymers as Medical Devices,” MedicalProducts and Biomaterials, March 1998.

[0054]FIG. 6 shows the plug 106A only partially filling the tube passage102, but it will be appreciated that the plug 106A may completely fillthe tube passage 106A. In that case, fluid flow would initially becompletely obstructed. Fluid flow begins only after the plug 106A hasbeen sufficiently absorbed to provide a path for fluid to flow out ofthe implant.

[0055] An absorbable plug may be used with any suitable configuration ofimplant, including implants with flow controlling rods or other flowcontrolling obstructions. Similarly, an absorbable plug may have anysuitable configuration and dimensions, selected in accordance with theflow characteristics that are desired. If desired, more than oneabsorbable plug may be used.

[0056] Some possible cross-sectional shapes for alternative absorbableplugs are shown in FIGS. 7A through 7D. Absorbable plug 106A has acircular cross-section. Absorbable plug 106B is similar to absorbableplug 106A with the addition of external grooves 108B. Absorbable plug106C has a flat surface 110C. Absorbable plug 106D has a longitudinalbore 112D. Alternative constructions include combining external groovesand internal bores, changing the number of them, and/or arranging themhelically or in any other suitable configuration. The absorbable plugmay be in a tapered or other suitable shape. It will be appreciated thatthe configuration of the absorbable plug will affect the absorption ofthe absorbable plug, with the areas in contact with the fluid beingabsorbed first.

[0057]FIG. 8 shows the use of an absorbable plug 106A in conjunctionwith partially occluded side holes 104. Each of the side holes 104 ispartially occluded by absorbable plugs 114, each of which has a centralbore 116. As with the absorbable plug 106A in the tube passage 102, theabsorbable plugs 114 in the side holes 104 may have any suitableconfiguration, and may be used in conjunction with any configuration ofabsorbable plug in the tube passage or with no absorbable plug in thetube passage.

[0058]FIGS. 9 through 11 show alternative mechanisms for partial and/ortemporary occlusion of the flow passage. In FIG. 9, the intraocularimplant 120 has a number of flow controlling strands 126 in the tubepassage 122. The flow controlling strands 126 serve to alter the flowcharacteristics through the implant, either partially or whollyobstructing flow through the implant. The number and/or size of thestrands may be varied as desired, and the strands may be of any suitablematerial. For example, ordinary sutures, such as polypropylene sutures,may be used.

[0059] At a period of time after implantation, one or more of the flowcontrolling strands 126 may be withdrawn from the implant (or advancedinto the implant). Further strands may be withdrawn (or advanced) atlater times. In this manner, the obstruction to flow through the implantcan be altered, at once or over a period of time, after the implantationprocedure has taken place.

[0060] It will be appreciated that the ability to withdraw or advanceone or more strands over time allows the physician to alter the flowcharacteristics of the implant in accordance with the needs of thepatient. For example, at a certain period of time after the implant hasbeen implanted in a patient's eye, the physician can check theintraocular pressure of the eye and determine whether one or morestrands should be withdrawn or advanced to increase or reduce flowthrough the implant. The patient can be checked periodically, and thestrands can be left in place, withdrawn or advanced as appropriate overa period of time.

[0061] The ability to withdraw strands is useful in the event theimplant should become clogged. In such a case, the physician canwithdraw one or more strands in order to restore proper flow through theimplant.

[0062]FIG. 10 shows an end view of an implant with a plurality of flowcontrolling strands 126 in the tube passage 122. It will be appreciatedthat the strands 126 may be arranged within the tube passage 122 in anysuitable manner, and the shape and configuration of the strands 126 arenot limited to that shown. For example, the strands may have differentcross-sections (e.g., oval, semi-circular, irregular, hollow, etc.) anddifferent sizes. The cross-sectional shapes and dimensions may varyalong the length of a single strand. Each of the strands in a singleimplant may have different configurations, e.g., differentcross-sectional shapes and/or dimensions. With different strands in theimplant, the physician can selectively withdraw (or advance) theappropriate strand or strands in accordance with the desired flowcharacteristics. For example, if a small increase in flow is desired, astrand with a small cross-section can be withdrawn, and if a largerincrease in flow is desired, a strand with a larger cross-section can bewithdrawn.

[0063]FIG. 11 shows an implant in which a single flow controlling strand128 having a knot 130 is placed within the tube passage 122. The knot130 serves to increase the flow obstruction. Alternatively, a plug orother obstruction may be attached to the strand 128, and more than onestrand 128 with a knot, plug or other attached obstruction may be used.Similar to the use of strands of different shapes and/or sizes, strandsmay be used having knots or plugs of different shapes and/or sizes,allowing selective withdrawal or advancement of the appropriate strandor strands in accordance with the desired flow characteristics.

[0064]FIG. 12 shows an alternate construction of a flow controllingstrand 132 in which the cross-sectional size of the strand varies alongits length. The illustrated strand 132 has three different sections.Section 138 on the end of the strand has the smallest diameter, theadjacent section 136 has a slightly larger diameter, and the remainder134 of the strand has an even larger diameter. The remainder 134 of thestrand may be sized to correspond to the diameter of the tube passage,with the sections 136 and 138 being incrementally smaller. Thus, with atube passage having a diameter, for example, of 100 microns, the strandmay also have a diameter of 100 microns, with incremental steps down to,for example, 20 microns. Of course, other dimensions may be used, andthe remainder 134 of the strand need not have the same size as the tubepassage. In the initial positioning, the strand 132 is located in thetube passage of the implant with the section 138 near the inlet end andwith part of the section 134 located within the tube passage near theoutlet end. When it is desired to increase the flow in the implant, thestrand 132 may be partially withdrawn such that only section 134 comesout of the tube passage. Thus, the obstruction within the tube passageis decreased, thereby increasing the flow. Later, if desired, the othersections may be successively withdrawn. Alternatively, the strand may befurther advanced into the tube passage to further constrict flow.

[0065] Variations of the strand shown in FIG. 12 are possible, with thesections being aligned along the strand in any desired pattern. Theconcept of a single strand which may be partially withdrawn or advancedin successive increments to vary the flow in steps may additionally oralternatively be achieved by using knots or plugs of different shapesand/or sizes along the length of a strand.

[0066] A flow controlling strand in accordance with the invention may becompletely separate from the implant and inserted into the implant someperiod of time after implantation, or the strand may be partially in theimplant upon implantation, with the option of advancing it further intothe implant at a later time.

[0067] An implant having withdrawable (and/or advanceable) flowcontrolling strands may be implanted using a delivery device 30 as shownin FIG. 2A. In such a case, the strands that extend out of the outletend of the implant may be accommodated in the central bore 36 of thedelivery device 30. Alternatively, with a suitably sized opening 40 inthe wall of the tube 34 of the delivery device 30, the strands may passoutside of the delivery device 30.

[0068] When the implant is implanted in an eye, the flow controllingstrands can be oriented to extend under the conjunctiva away from theimplant. The strands used may be long enough to extend out of theimplant beyond the slit made in the conjunctiva for inserting theimplant. In this case, after implanting the implant, the physician cantuck the loose ends of the strands under the conjunctiva to extend awayfrom the slit. When it is desired to withdraw one or more of thestrands, a small slit can be made in the conjunctiva near the ends ofthe strands, and the strands can be pulled through that slit. Becausethese ends are remote from the implant and the prior slit made in theconjunctiva, the potential trauma to the eye is reduced.

[0069] To fix the strands in place and facilitate later access to them,the loose ends may be sutured to the adjacent tissue, e.g., the sclera.This may be done either with additional sutures or with the strandsthemselves. In the latter case, suturing needles may be attached to theloose ends of the strands to facilitate suturing of the strands afterimplantation of the implant.

[0070] It will be appreciated that various features of theabove-described embodiments may be combined as desired. For example, theflow controlling strands may be made of absorbable material, leaving theoption of having a physician physically withdraw the strands or allowingthem to be absorbed. Additionally or alternatively, plugs or otherobstructions secured to the strands may be made of absorbable material.Different strands, plugs or obstructions may be made from materials withdifferent rates of absorption, and/or they may be made from acombination of materials with different rates of absorption.

[0071] As will also be appreciated by persons having ordinary skill inthe art, the various embodiments of implants, methods of manufacture,delivery devices, and methods for implantation described hereinabove aregiven by way of example only. Various changes, modifications andvariations may be applied to the described embodiments without departingfrom the scope of the invention, defined by the appended claims.

What is claimed is:
 1. An implant in combination with a delivery devicefor implanting the implant, wherein the implant comprises a tube and anoutwardly extending retention projection, wherein the delivery devicecomprises a tube having an outside surface and a central bore foraccommodating the implant, and wherein the delivery device has anopening in the side of the tube allowing the retention projection toproject beyond the outside surface of the tube of the delivery device.2. An implant and delivery device according to claim 1, wherein theimplant is formed of plastic.
 3. An implant and delivery deviceaccording to claim 1, wherein the retention projection is located at aninlet end of the implant, and wherein the implant further comprises anouter flange located at an outlet end of the implant.
 4. An implant anddelivery device according to claim 3, wherein the opening in the side ofthe tube of the delivery device also allows the outer flange of theimplant to project beyond the outside surface of the tube of thedelivery device.
 5. An implant and delivery device according to claim 3,wherein the outer flange of the implant is resilient so that it may beaccommodated within the central bore of the tube of the delivery device.6. An implant in combination with a delivery device for implanting theimplant, wherein the implant comprises a tube having an inlet end and anoutlet end and an outwardly extending retention projection, wherein thedelivery device comprises a tube having an outside surface, a centralbore for accommodating the implant and an opening at one end forallowing the implant to exit the central bore, and wherein the implantis accommodated within the central bore with its inlet end closer to theopening than its outlet end so that the inlet end of the implant exitsthe central bore of the delivery device before the outlet end.
 7. Animplant and delivery device according to claim 6, wherein the implant isformed of plastic.
 8. An implant and delivery device according to claim6, wherein the retention projection is located proximate the inlet endof the implant, and wherein the implant further comprises an outerflange located proximate the outlet end of the implant.
 9. An implantand delivery device according to claim 8, wherein the outer flange ofthe implant is resilient so that it may be accommodated within thecentral bore of the tube of the delivery device.
 10. An implant anddelivery device according to claim 6, wherein the retention projectionof the implant is resilient so that it may be accommodated within thecentral bore of the tube of the delivery device.
 11. A delivery devicefor use in implanting an implant, wherein the delivery device comprisesa tube having an outside surface and a central bore for accommodatingthe implant, and wherein the delivery device has an opening in the sideof the tube allowing a retention projection of the implant to projectbeyond the outside surface of the tube of the delivery device.
 12. Adelivery device according to claim 11, wherein the opening in the sideof the tube of the delivery device also allows an outer flange of theimplant to project beyond the outside surface of the tube of thedelivery device.
 13. A method of implanting an implant, comprising thesteps of: placing the implant in a central bore of a delivery device,said placing step including allowing a retention projection of theimplant to project beyond an outer surface of a tube of the deliverydevice; inserting the delivery device with the implant placed in thedelivery device through tissue into which the implant is to beimplanted; and withdrawing the delivery device, leaving the implantimplanted in the tissue.
 14. A method of implanting an implant,comprising the steps of: placing the implant in a central bore of adelivery device, said placing step including positioning the implant sothat the implant is accommodated within the central bore with an inletend of the implant closer to an opening in the delivery device than anoutlet end of the implant; inserting the delivery device with theimplant placed in the delivery device through tissue into which theimplant is to be implanted; and withdrawing the delivery device, leavingthe implant implanted in the tissue.
 15. A method of manufacturing aflow control device comprising the steps of: providing a mold having acavity with a generally tubular shape; positioning a wire within themold such that the wire is suspended to extend along a longitudinal axisof the generally tubular shaped cavity; putting a moldable material intothe mold; and allowing the moldable material to harden such that ithardens in the generally tubular shape of the mold, with a longitudinaltube passage formed in the hardened material on account of the wirepositioned in the mold.
 16. An implant for regulating fluid flowcomprising: a tube comprising an inlet end, an outlet end, and a tubepassage extending between the inlet end and the outlet end forpermitting fluid to flow through the tube passage; and absorbablematerial located within the tube passage, wherein initially theabsorbable material serves to partially or wholly obstruct flow throughthe tube passage and wherein the absorbable material erodes as itcontacts fluid such that the obstruction of flow through the tubepassage is reduced over time.
 17. An implant according to claim 16,wherein initially the absorbable material substantially fills the tubepassage so as to prevent flow through the tube passage.
 18. An implantaccording to claim 16, wherein initially the absorbable materialpartially fills the tube passage so as to allow partial flow through thetube passage.
 19. An implant for regulating fluid flow comprising: atube comprising an inlet end, an outlet end, and a tube passageextending between the inlet end and the outlet end for permitting fluidto flow through the tube passage; and one or more flow controllingstrands located within the tube passage, wherein initially the one ormore flow controlling strands serve to partially or wholly obstruct flowthrough the tube passage and wherein at least one flow controllingstrand may be displaced with respect to the tube passage to change theobstruction of flow through the tube passage.
 20. An implant accordingto claim 19, wherein initially the one or more flow controlling strandssubstantially fill the tube passage so as to prevent flow through thetube passage.
 21. An implant according to claim 19, wherein initiallythe one or more flow controlling strands partially fill the tube passageso as to allow partial flow through the tube passage.
 22. An implantaccording to claim 19 further comprising a plug attached to one or moreof said flow controlling strands.
 23. An implant according to claim 19wherein one or more of said flow controlling strands has a knot in it.24. An implant according to claim 19, wherein at least one flowcontrolling strand may be withdrawn from the tube passage to reduce theobstruction of flow through the tube passage.
 25. An implant accordingto claim 24, wherein at least one flow controlling strand may becompletely withdrawn from the tube passage to reduce the obstruction offlow through the tube passage.
 26. An implant according to claim 24,wherein at least one flow controlling strand may be partially withdrawnfrom the tube passage to reduce the obstruction of flow through the tubepassage.
 27. An implant according to claim 19, wherein at least one flowcontrolling strand may be advanced within the tube passage to increasethe obstruction of flow through the tube passage.
 28. An implantaccording to claim 19 comprising at least two strands.
 29. An implantaccording to claim 28, wherein two of the strands have differentcross-sectional dimensions.
 30. An implant according to claim 28,wherein each of at least two strands has a plug attached to it, with theplugs on the at least two strands having different cross-sectionaldimensions.
 31. An implant according to claim 28, wherein each of atleast two strands has a knot in it, with the knots in the at least twostrands having different dimensions.
 32. An implant according to claim19 wherein at least one flow controlling strand has different areasalong its length with different cross-sectional dimensions.
 33. Animplant according to claim 19 wherein at least one flow controllingstrand is made of absorbable material.
 34. An implant for regulatingfluid flow comprising: a tube comprising an inlet end, an outlet end,and a tube passage extending between the inlet end and the outlet endfor permitting fluid to flow through the tube passage; and means fortemporarily obstructing, in whole or in part, fluid flow through thetube passage.
 35. An implant according to claim 34 wherein the means fortemporarily obstructing, in whole or in part, fluid flow through thetube passage comprises absorbable material located in the tube passage.36. An implant according to claim 34 wherein the means for temporarilyobstructing, in whole or in part, fluid flow through the tube passagecomprises at least one flow controlling strand located in the tubepassage.